1. Field of the Invention
The present invention pertains to an ultrasonic diagnosis apparatus. More particularly, the present invention relates to an ultrasonic diagnosis apparatus for, when ultrasonic beams are scanning in a living body, setting optimal transmission conditions for such each scanning line, achieving a uniform image quality over an image, and providing effective information for analysis on an application site.
2. Description of Related Art
An ultrasonic diagnosis apparatus for obtaining an image signal by transmitting and receiving an ultrasonic signal to/from a subject is used in a variety of modes utilizing noninvasive properties of such an ultrasonic signal. This ultrasonic diagnosis apparatus is mainly of type acquiring a tomographic image of soft tissues of a living body using an ultrasonic pulse reflection technique. There is a variety of imaging techniques based on this ultrasonic pulse reflection technique. In recent years, as one of such techniques, there has been paid special attention to a technique called xe2x80x9charmonic imagingxe2x80x9d for imaging a high harmonics component that is a non-basic component in an ultrasonic echo signal.
The harmonic imaging includes a technique called THI (Tissue Harmonic Imaging) for sampling and imaging a high harmonics component caused by distortion of waveforms of such ultrasonic pulses while ultrasonic pulses propagates a living organ; and a technique (hereinafter, referred to as a xe2x80x9ccontrast echoxe2x80x9d) using a contrast echo technique for sampling and imaging a contrast medium-derived high harmonics component caused by the fact that micro-bubbles (very small air bubbles) such as levobist being a main component of the contrast medium are stronger in acoustic non-linearity than a living organ, and generates many more high harmonics components.
In the case of the THI, a signal of such high harmonics component is not directly transmitted from a transducer, and is generated by the transmitted ultrasonic pulses propagating from the oscillator by a proper distance. Thus, multiple echoes from an obstacle located immediately beneath the vibrator (for example, ribs when a circulatory region is scanned from a site between ribs) are significantly reduced. In addition, more high harmonics components are generated at a site at which a sound pressure is high. Thus, the beam in a focus direction, i.e., a main lobe is enhanced, and conversely, a side lobe is reduced. As a result, a profile of a sound field beam with its excellent directivity is formed. Therefore, according to a THI having such characteristics, there is provided an advantage that a noise due to multiple reflection or side lobe artifact is reduced, and thus, an image quality is improved, and, for example, the boundary of organs and contrast ratio are improved.
On the other hand, in the case of the contrast echo, a nonlinear component relevant to a basic transmission frequency, in particular, a reflection echo signal of a secondary harmonics component, is detected, and signal levels are discriminated between organs where harmonics are hardly generated. For example, a reflection echo signal includes a basic frequency component of a transmission pulse wave and a harmonics component caused by micro-bubbles that is a main component of contrast medium. Thus, by sampling only such harmonics component from the reflection echo signal, a signal ratio of a contrast medium echo signal to a living organ echo signal is remarkably improved, and an image including a harmonics component, i.e., degree of enhancement caused by contrast medium can be obtained. Therefore, according to a contrast echo having such characteristics, the presence or absence of contrast medium in a region of interest, i.e., a blood flow perfusion or the like, can be observed merely by administrating a comparatively small amount of contrast medium, and information useful for diagnosis is obtained.
In the case of harmonics imaging such as the described THI or contrast echo, the following inconveniences have occurred as compared with a vase of imaging caused by general B mode scanning.
In general, in a sector probe generally used in examination of circulatory organs using an ultrasonic diagnosis apparatus, transmission conditions are identical in scanning lines, each of which configures an image. If a beam deflection angle is greater, the following phenomenon that a transmission sound field differs depending on scanning lines occurs because: 1) a sound pressure of transmission beams formed on scanning lines is reduced; and 2) a beam width increases as compared with a case in which transmission beams are not deflected, and spatial resolution is degraded. Thus, in a conventional B mode scan of ultrasonic beam, in order to take countermeasures against the phenomenon, there is employed a technique for adjusting an image quality such as a receiving gain every scanning line from a receive signal from a non-uniform transmission sound field, thereby generating more uniform images.
However, such countermeasures assume a case of a general B mode image, failing to assume a case of harmonics imaging such as THI or contrast echo.
That is, in harmonics imaging, a transmission sound field, in particular, a sound pressure becomes an important factor relevant to sensitivity, and there is a limitation to compensating for non-uniformity of a transmission sound field by adjustment of a received image quality. Thus, the uniformity of the transmission sound field is required for fully achieving these advantageous effects. The intensity of the harmonics component is proportional to a square of the sound pressure, and thus, a receiving gain having a square in amplitude must be corrected as compared with a conventional B mode. A change in such receiving gain causes a change in noise level, thereby producing a non-uniform image with its different noise level in image.
In harmonics imaging, such tendency is more significant in the case of a contrast echo utilizing micro-bubbles (for example, levobist) that is a contrast medium. That is, in the case of THI, even if the transmission sound pressure is low, although the receiving gain is increased concurrently, whereby a noise component increases in proportional to such increase, sampling/correction of a high harmonics component is possible. In contrast, in the case of contrast echo, if the transmission sound pressure is low, micro-bubbles to be detected may not make a nonlinear response. In such a circumstance, even if the receiving gain is increased to the maximum, it is difficult to detect a micro-bubble derived high harmonics component.
In addition, the beam width generally increases as the transmission beam deflection angle increases irrespective of whether or not harmonics imaging is carried out. With respect to this phenomenon, the non-uniformity of spatial resolution occurs. In particular, in the case of parallel, simultaneous receiving, there is a possibility that a phenomenon such as beam curving is increased.
The foregoing problems apply to another probe such as linear probe as well as sector probe. That is, these problems apply to all the probes that undergo scanning under the same transmission conditions, although actual transmission sound fields are different from each other relevant to a respective one of the scanning lines in order to form the same transmission beams.
The present invention has been made in view of the foregoing conventional problems. It is a primary object of the present invention to provide an ultrasonic diagnosis apparatus for scanning the inside of a living body by using electronic scanning, and generating and displaying an image, wherein an entirely uniform image quality with its less non-uniformity is achieved, and more useful information is provided by diagnosis at a clinical application site.
It is another object to achieve an entirely uniform image quality with its less non-uniformity, and to provide more effective information for diagnosis at a clinical application site in the case of harmonics imaging such as THI or contrast echo as well.
In order to achieve the foregoing objects, according to the present invention, there is provided an ultrasonic diagnosis apparatus comprising: a transmission condition controller configured to set transmission conditions that are difference according to a scanning direction of ultrasonic beams so as to correct non-uniformity of a transmission sound field for each scanning region in scanning of the ultrasonic beams; a ultrasonic transmitter configured to transmit the ultrasonic beams to a subject under the transmission conditions set by the transmission condition controller; and an image generator configured to obtain a ultrasonic image of the subject from a ultrasonic echo signal reflected from the subject of the ultrasonic beams transmitted by the ultrasonic transmitter.
In the present invention, the ultrasonic transmitter can be configured to change the transmission conditions in one image mode.
In the present invention, the transmission conditions can be at least one of a transmission aperture, a transmission aperture area, a transmission aperture position, a transmission aperture shape, a transmission sound pressure, a transmission pulse wave form, a frequency distribution condition for transmission ultrasonic wave, a focus, a transmission element distribution, and a transmission aperture weighting function.
In the present invention, the transmission condition controller can be a controller configured to set the transmission sound pressure or MI (Mechanism Index) value in the scanning region to be uniform or setting the transmission sound pressure or MI value in a virtual face vertical to the scanning line to be uniform.
In the present invention, the image generator can comprise a measure configured to measure an index concerning a transmission sound field for such each scanning direction from the ultrasonic echo signal. The average intensity of echo signals on scanning lines each or its center frequency is exemplified for the index concerning the transmission sound field.
In the present invention, the image generator can comprise a display configured to display the index measured by the measure.
In the present invention, the transmission condition controller can comprise a controller configured to set the transmission condition based on the index measured by the measure.
In the present invention, the transmission condition controller can comprise a controller configured to enable an operator to set the transmission conditions.
In the present invention, the ultrasonic transmitter can comprise a pulsar in number that is smaller than the number of transmission scanning lines along the scanning direction and a transmitter for transmitting ultrasonic waves under transmission conditions different depending on each direction of the scanning while such each pulsar is switched.
In the present invention, a controller configured to change receiving conditions for such each scanning direction can be further provided.
In the present invention, a generator configured to generate an image by a plurality of transmissions relevant to the scanning direction can be further provided.
According to another aspect of the present invention, there is provided an ultrasonic diagnosis apparatus comprising: a transmission condition controller configured to set transmission conditions that are different according to a scanning direction of the ultrasonic beams so as to correct non-uniformity of a transmission sound field in a scanning region in scanning of ultrasonic beams in one frame; a ultrasonic transmitter configured to transmit the ultrasonic beams to a subject under transmission conditions set by the transmission condition controller; and an image generator configured to sample a harmonics component from a ultrasonic echo signal reflected from the subject of the ultrasonic beams transmitted by the ultrasonic transmitter, thereby obtaining a harmonic ultrasonic image of the subject.
According to still another aspect of the present invention, there is provided an ultrasonic diagnosis apparatus comprising: a transmission condition controller configured to set transmission conditions that are different according to a scanning direction of the ultrasonic beams based on manual operation of an operator so that a transmission sound field for each scanning region enters a desired state in scanning of ultrasonic beams in one frame; a ultrasonic transmitter configured to transmit the ultrasonic beams under transmission conditions set by the transmission condition controller; and an image generator configured to obtain a ultrasonic image of the subject from a ultrasonic echo signal reflected from the subject of the ultrasonic beams transmitted by the ultrasonic transmitter.
According to still another aspect of the present invention, there is provided an ultrasonic diagnosis apparatus comprising: a transmission condition controller configured to set transmission conditions that are different according to a scanning direction of the ultrasonic beams so as to correct non-uniformity of a transmission sound field for each scanning region in scanning of transmission beams in one frame; a receiving condition corrector configured to correct receiving conditions of the ultrasonic beams according to transmission conditions set by the transmission condition controller; a ultrasonic transmitter configured to transmit the ultrasonic beams to a subject under transmission conditions set by the transmission condition controller; and an image generator configured to obtain a ultrasonic image of the subject under receiving conditions corrected by the receiving condition corrector from a ultrasonic echo signal reflected from the subject of ultrasonic beams transmitted by the ultrasonic transmitter.
In the present invention, the transmission condition controller can have a selector configured to select type of contrast medium and a controller configured to set the transmission conditions according to the contrast medium selected by the selector. The type of contrast medium used here includes levovist, optison, and sonosoid or the like, for example.
According to the present invention, transmission conditions are optimally set according to purposes for each scanning line, and partial image degradation is prevented, thereby generating an image having its uniform image quality. In particular, an image with its high image quality suitable to case of harmonics imaging such as THI or contrast echo can be obtained.
The other configuration and advantageous effects according to the present invention is evident from a description based on the following embodiments and accompanying drawings of the invention.